Content & Privacy Restrictions have no effect on MacOS

I have been testing the content and privacy restrictions in Mac OS 10.5.7 (19H1615).

1. Click Preferences->Screen Time->Content & Privacy.
2. Click "turn on"
3. Click "Limit Adult Websites"
4. Open Safari (or any browser) and navigate to pornhub.com. Site loads normally. Nothing is not blocked.
5. Go back to Preferences->Screen Time->Content & Privacy.
6. Click "customize"
7. Add any website (e.g. twitter.com)
8. Open Safari and navigate to twitter.com. Site loads fine. Nothing is not blocked.
9. Repeat in Chrome. Nothing is blocked.
10. Restart computer, check again. Nothing is blocked.

So basically content restriction doesn't work. At all. In any way. Is anyone else experiencing this? Does anyone know how to fix it?

Notes: family sharing is turned off. I haven't tried this on a phone.